As means for slicing off a wafer from a semiconductor ingot, a wire saw has been conventionally known. In the wire saw apparatus, a slicing wire is wound around a plurality of wire guides many times to form a wire row, the slicing wire is driven in an axial direction at a high speed, a workpiece is fed to the wire row for cutting while appropriately supplying slurry containing free abrasive grains of silicon carbide or the like, and this workpiece is thereby sliced to respective wire position at the same time.
In more detail, a slice base extending over an entire region along the axial direction is secured to a part of the workpiece in a circumferential direction, the entire workpiece is fed for slicing in a state where this slice base is held in a workpiece holder, and it is sliced by the cutting wire from a side opposite to the slice base. At this time, as to a direction along which the workpiece is pressed against the wire row, a method for pressing the workpiece against the wire row from above and a method for pressing the same from below are known, but a method for pressing the workpiece against the wire row from above is the mainstream in slicing of a semiconductor silicon ingot.
Further, there is also recently adopted a method for performing slicing while supplying a coolant only with the use of a wire having diamond abrasive grains fixed on a wire surface thereof in place of supplying slurry containing free abrasive grains. The method for supplying the slurry containing free abrasive grains will be referred to as a free abrasive grain system, and the method using the wire having diamond abrasive grains fixed on the wire surface thereof will be referred to as a fixed abrasive grain system hereinafter.
Here, FIG. 3 shows an overview of a general wire saw apparatus.
A wire saw apparatus 101 includes a wire 103 to slice a workpiece 102, at plurality of wire guides 104 around which the wire 103 is wound, a wire tension applying mechanisms 105 and 105a to apply tensile force to the wire 103, a workpiece feed mechanism 106 which holds the workpiece 102 to be sliced and feeds it downward, and a nozzle 107 which supplies a coolant or slurry at the time of slicing.
A working fluid supply mechanism 108 is constituted of the nozzle 107, a tank 109, a chiller 110, and others. The nozzle 107 is installed above a wire row 103a to be orthogonal to the wire row 103a. The nozzle 107 is connected to the tank 109, and the coolant or the slurry can be stirred in the tank 109, subjected to temperature control by the chiller 110, and then supplied from the nozzle 107 to the wire 103.
The coolant or the slurry is supplied in a curtain-like manner through a slit with a fixed width provided in a lower surface of the nozzle 107 so that it can be uniformly supplied to each wire 103 in the wire row 103a. Further, the coolant or the slurry is fed to a slicing portion of the workpiece 102 through the wire row 103a. Then, the supplied coolant or slurry is returned to the tank 109 and recycled.
The wire 103 is reeled out from one wire reel 111, fed to the wire tension applying mechanism 105 formed of a torque motor 113 or the like via a traverser 112, and reaches the wire guides 104. The wire 103 is wound around the wire guides 104 for approximately 300 to 400 times so that it travels in an axial direction to form the wire row 103a, and is then taken up by a wire reel 111a through the other wire tension applying mechanism 105a including a torque motor 113a and a traverser 112a. 
When the workpiece 102 is sliced into a wafer shape by using such a wire saw apparatus 101 and a shape of the sliced wafer is checked, a large warp is produced in some situations. The warp is one of important qualities in slicing of the semiconductor wafer, and a further reduction is demanded as a request for product, quality is increased.
It has been revealed that, of warps produced due to slicing of the workpiece 102, one which is produced in a latter half part of slicing is greatly affected by scattering of the supplied slurry. Thus, a measure has been taken to reduce an influence of spatter of the scattered slurry by taking a large distance between a lower end surface of a workpiece holding section and an upper surface of a workpiece as disclosed in Patent Literature 1, or to reduce the influence by controlling a scattering direction of the slurry as disclosed in Patent Literature 2 and Patent Literature 3.